ECG Flashcards
What does an electrical current towards the probe show as on an ECG? And away?
towards- positive
away - negative
What does the QRS complex represent?
ventricular depolarisation
What is the normal time for a QRS complex
0.04- 0.12
What does the P wave represent?
atrial depolarisation time
How tall should the P wave be and how long should the P wave be ?
0.1 sec
no more than 2.5mm tall
Where can the p wave be seen the tallest?
lead 2
What does the T wave represent?
ventricular repolarisation
how tall should the T wave be?
5-10mm
What is the U wave?
repolerisation of the purkinje fibers and is often not seen
What is an interval
length of the plus the isoelectric line that follows it
What is the PR interval ?
space between the beginning of the wave and the beginning of the QRS complex
What is the normal time of an PR interval ?
3-5 small squares (0.12-0.2)
What is the QT interval ?
from the beginning of the QRS complex to the end of the T wave
IF U wave presence all the way to the end of the u wave
What is the ST segment?
isoelectric line betweeen the end of the S wave of the QRS complex and beginning of the T wave
What is the PR segment?
from the end of the P wave the beginning of the Q wave
represents the conduction from when the atria are depolarised to the ventricular depolarisation.
What is the time of one small square and big square
small square -0.04
big square is 0.2
What is the height of one small square?
small square- 0.1mV
larger square 0.5mV
How do you estimate the rate ?
Approach 1:
- count the R waves in 10sec
- times it by 6
Approach 2:
1. count the large squares between 2 R waves
1 -300 2-150 3- 100 4- 75 5- 60 6-50
How do you measure the rhythm?
look if the RR interval is the same across the whole strip
What do you look at to suspect a bundle branch block?
look at the QRS complex- anything longer 0.12 too much.
How do you distinguish a right and left bundle branch block?
look at lead V1.
left - downwards deflected
right- upwards deflected
What is a first degree AV block
PR interval longer than 0.2 seconds
What can cause a bundle branch block
pericarditis, myocarditis, congested heart failure and congenital heart disease
What can cause a first degree AV block?
coronary heart disease inferior wall MI hyperkalaemia congenital abnormalities medications (quinidine, digitalis, beta blockers, calcium channel blockers)
What is a second degree AV block type 1 (Mobitz)?
progressive delay of conduction at the AV node until conduction is blocked - resulting in no QRS complex
What are the characteristics of the second degree AV block type 1 (Mobitz type 1)
- rate is 60-100 beats per minute
- atrial rhythm is regular
- ventricular rhythm is irregular
- P wave normal
- PR interval get longer until QRS is droppped
- QRS is normal just gets dropped every onceand a while
What is a second degree AV block type 2 (Mobitz type 2)?
2-4 P wave before each QRS
What are the causes of the second degree AV block type 1 (Mobitz type 1)
acute inferior wall myocardial infarction
digitalis
rheumatic fever
myocarditis
excissive vagal tone
drugs (beta blockers, calcium channel blockers)
What are the characteristics of the second degree AV block type 2 (Mobitz type 2)
Atrial and ventricular rate irregular
several p waves
What are the causes of the second degree AV block type 2 (Mobitz type 2)
acute anterior or antero septal myocardial infarction
coronary heart disease
rheumatic heart disease
drugs (beta blockers, calcium channel blockers)
What are the characteristics of the second degree AV block type 2 (Mobitz type 2)
atrial rate is faster than ventricular rate
no relationship between QRS and P wave
What happens in a third degree AV block
electrical signals from SA node are completly blocked at the AV node
-> no coordination between contraction of the atria and ventricles
What is an ST elevation due to?
impending infarction
also due to pericarditis, vasospastic angina
- laso can be normal
What are the characteristics of an ST elevation ?
if it exceeds 1mm in a limb lead or 2 mm in a precordial lead
What happens in a transmural infarction to the ST elevation?
ST elevation one of the first signals
- as time passes the st elevation decreases due to the T wave inversion
What happens in a ventricular aneurysm to the ST elevation?
- ST elevation remains even after 3 months
What do you do if an ST elevation persists after 3 months?
ventricular aneurysm-
don’t give thrombolytic drugs
What is vasospastic angina
during exercise you get vasospasm and lack of blood flow to the subendocardium
-> lack of blood flow to the transmural area of the heart _> ST elevation
What is Pericarditis ?
inflammation pf the space between the heart and the pericardial sack
What are signs of pericarditis on an ECG?
ST elevation
What is early repolerisation?
T wave occurs early and leads to ST elevation
HARMLESS
can be seen well in the precordial leads and less in the limb leads
IN what individuals do you get early re-polarisation?
young healthy males
What leads do you use for the axis nomenclature?
lead 1 and aVF because they are perpendicular to each other
What is the normal range for an normal axis?
-30 to 90
What is the range for an left axis deviation?
-30 to -90
What is the range for a right axis deviation?
90 to +or -180
What disease does a left axis deviation indicate
inferior wall MI
What disease does a right axis deviation indicate
lateral wall MI
